Recording media for recording music content, video data, and other such digital data come in many different forms, such as magnetic disks, optical disks, and opto-magnetic disks. Of these recording media, a memory card in which a flash ROM or other such semiconductor memory is used as a recording element allows the recording medium to be more compact, so such memory cards are rapidly gaining popularity, especially in compact portable devices such as digital still cameras and portable telephone terminals. Recently, semiconductor memories are being used also in applications as built-in storage for devices, and not just applications as removable media such as conventional memory cards. For example, a flash ROM or other such semiconductor memory is built into a device and used instead of a hard disk.
Meanwhile, recent years have seen an increase in public access points that afford connectivity, such as train stations and coffee shops, while the trend toward wireless home networks is rapidly making wireless LAN connection environments more popular. Along with this, devices compatible with a wireless LAN are quickly catching on, along with the numbers and types of terminals, such as portable telephone terminals, tablet terminals, NAS (network attached storage), and HDD recorders, in addition to the notebook personal computers that were the mainstream in the past.
In light of this popularity of wireless LAN, there have been proposed memory cards equipped with a wireless function, in which a wireless function is installed in a conventional memory card (see Patent Literature 1, for example). These memory cards with a wireless function have the same interface shape as a conventional memory card, so the interface can be shared with a host device having a slot for a conventional memory card. Furthermore, memory cards with a wireless function make wireless compatibility possible at low cost, without having to install hardware or software resources for wireless communication on the host device side.
For example, when a memory card is mounted in a digital still camera, in the past the memory card first had to be taken out of the digital still camera and put into a PC or the like to upload still pictures to a Web service or the like. With a memory card having a wireless function, however, the host device can be easily networked, allowing still pictures to be uploaded to a Web service directly from the digital still camera, for example.
Furthermore, installing wireless communication function in a memory card allows direct wireless connection between memory cards, so that file sharing becomes possible. Consequently, a still picture captured at an event such as a sporting event or a wedding can be transferred to others right on the spot, making photograph sharing more convenient.
FIG. 14 shows an overview of file sharing. In file sharing, the first step is that a sending-side host device 30 (such as a digital still camera) notifies a sending-side card 40 (such as a memory card with a wireless function) of transfer destination information and the file name in question, and outputs a file transfer command. The sending-side card 40 then connects to a receiving-side card 41 (such as a memory card with a wireless function) on the basis of the received transfer destination. The sending-side card 40 then detects the file in question on the basis of the received file name, actually reads the file data, and sends the data to the receiving-side card 41. The receiving-side card 41 produces a file upon receiving the file data, and notifies a receiving-side host 31 (such as a digital still camera) that a file has been acquired.
In another method, file reading is carried out by the sending-side host 30, and the read data is sent from the sending-side host 30 to the sending-side card 40, so that processing of the file system is not performed within the sending-side card 40. However, if the configuration as shown in FIG. 14 is applied, in which the reading and sending of files is carried out within the sending-side card 40, there is no need for data transfer between the sending-side host 30 and the sending-side card 40, and file transfer can be faster.